Solid-state image sensor and driving method

ABSTRACT

There is provided a solid-state image sensor including a pixel circuit including a plurality of pixels and imaging a subject, a peripheral circuit provided in a vicinity of the pixel circuit and performing operation in regard to imaging, and a connection element electrically connecting, in initialization of the pixels, elements in the pixels to which a predetermined voltage is applied for initializing the pixels to the peripheral circuit with the predetermined voltage.

BACKGROUND

The present technology relates to a solid-state image sensor and adriving method, and specifically, relates to a solid-state image sensorand a driving method capable of suppressing increase in area of an imagesensor and reducing impedance of pixels.

For example, an image sensor which performs imaging by performingphotoelectric conversion on light incident from the subject causes adrop of power supply (voltage drop) in driving for initialization ofpixels, for example, in resetting the pixels constituting the imagesensor. Such a drop of power supply is known larger as the number ofpixels of the image sensor is larger.

Therefore, in order to relieve such a drop of power supply, there is atypical measure of reducing impedance by making power supply wirings forsupplying power to pixels and/or power supply wirings of the pixelsthemselves thick.

Moreover, there is also an image sensor in which two power supply linesas power supply wirings of a peripheral circuit of pixels are providedalong a signal processing part, interposing common signal lines, andthese power supply lines are connected with a cross connection line,this improving a signal readout speed (for example, see Japanese PatentLaid-Open No. 2008-054246).

Furthermore, there is also proposed an image sensor in which a pluralityof power supply parts capable of supplying a plurality of predeterminedpotentials are provided and the potentials supplied from these powersupply parts to pixels are selectively switched to distribute circuitload (for example, see Japanese Patent Laid-Open No. 2007-067682).

SUMMARY

However, in the above-mentioned technologies, making power supplywirings and the like thick in order to reduce impedance of the pixelscauses increase in wiring areas of the image sensor, that is, an area ofthe image sensor, resulting in increase of costs.

Moreover, the wiring way in which two power supply lines are providedand these power supply lines are connected with a cross connection linemeans making wirings surrounding the target circuit thick in order toreduce impedance of power supply, this causing the increase in wiringareas. Furthermore, the image sensor in which a plurality of powersupply parts for selectively switching supply potentials are providedbecomes large by the area in the image sensor which area corresponds tothese power supply parts.

It is desirable to provide an image sensor in which increase in areathereof can be suppressed and impedance of pixels can be reduced.

According to an embodiment of the present technology, there is provideda solid-state image sensor including a pixel circuit including aplurality of pixels and imaging a subject, a peripheral circuit providedin a vicinity of the pixel circuit and performing operation in regard toimaging, and a connection element electrically connecting, ininitialization of the pixels, elements in the pixels to which apredetermined voltage is applied for initializing the pixels to theperipheral circuit with the predetermined voltage.

The connection element electrically may separate the elements from theperipheral circuit while the peripheral circuit is performing operationin regard to imaging, the operation being different from theinitialization of the pixels.

The predetermined voltage may be a positive voltage.

The peripheral circuit may be connected to power supply supplying powerat the predetermined voltage. And the connection element temporarily mayconnect the elements to the power supply by connecting the elements tothe peripheral circuit in the initialization of the pixels.

The solid-state image sensor may further include a power supplycontroller supplying power at the predetermined voltage to theperipheral circuit in the initialization of the pixels, and supplyingpower at a voltage different from the predetermined voltage to theperipheral circuit when the peripheral circuit is performing theoperation in regard to imaging, the operation being different from theinitialization of the pixels.

The predetermined voltage may be a negative voltage or zero.

According to an embodiment of the present technology, there is provideda driving method of a solid-state image sensor including a pixel circuithaving a plurality of pixels and imaging a subject, a peripheral circuitprovided in a vicinity of the pixel circuit and performing operation inregard to imaging, and a connection element connecting elements in thepixels to the peripheral circuit, the method including electricallyconnecting, by the connection element, in initialization of the pixels,the elements in the pixels to which a predetermined voltage is appliedfor initializing the pixels to the peripheral circuit with thepredetermined voltage.

According to one embodiment of the present technology, there is provideda solid-state image sensor including: a pixel circuit having a pluralityof pixels and imaging a subject; a peripheral circuit provided in thevicinity of the pixel circuit and performing operation in regard toimaging; and a connection element connecting elements in the pixels tothe peripheral circuit, the connection element electrically connecting,in initialization of the pixels, the elements in the pixels to which apredetermined voltage is applied for initializing the pixels to theperipheral circuit with the predetermined voltage.

According to one embodiment of the present technology, increase in areaof an image sensor can be suppressed and impedance of pixels can bereduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining a power supply drop;

FIG. 2 is a diagram illustrating an exemplary configuration of asolid-state image sensor;

FIG. 3 is a diagram for explaining reduction of the power supply drop;

FIG. 4 is a diagram illustrating an exemplary configuration of thesolid-state image sensor;

FIG. 5 is a diagram for explaining reduction of the power supply drop;and

FIG. 6 is a diagram illustrating an exemplary configuration of an imagecapturing apparatus.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the appended drawings, structural elementsthat have substantially the same function and structure are denoted withthe same reference numerals, and repeated explanation of thesestructural elements is omitted.

First Embodiment [Summary of Present Technology]

First, summary of the present technology is described.

A larger number of pixels in an image sensor (solid-state image sensor)and/or driving in a shutter method in which exposure periods for all thepixels are coincident with one another increase the number of pixelswhich are reset simultaneously, this leading to an increase of a drop ofpixel power supply caused by the reset of the pixels.

For example, as indicated by the curve C11 in FIG. 1, in case where asmall number of pixels are reset simultaneously, although a drop ofpixel power supply (an instant decrease of pixel power supply) takesplace caused by the reset of the pixels, the decrease in voltage is justsmall. In addition, in FIG. 1, the horizontal direction corresponds totime and the vertical direction corresponds to voltage of the pixelpower supply. Moreover, the position of the arrow RT11 in the horizontaldirection in the figure indicates the time point when the pixels arereset.

The voltage of the pixel power supply indicated by the curve C11slightly decreases at the time of the reset of the pixels, and afterthat, recovers immediately. Herein, the voltage of the pixel powersupply is a voltage applied to a reset transistor, for example, forsetting the potential of a floating diffusion region in each pixel tothe level of a reset voltage, that is, a voltage of a power supplyconnected to the reset transistor.

On the contrary, in case where a large number of pixels are resetsimultaneously, as indicated by the curve C12, the voltage of the pixelpower supply significantly decreases at the time of the reset of thepixels, and it takes time until the voltage recovers.

As mentioned above, when wirings in the pixels and/or wirings to thepixels are made thick to reduce impedance of the pixels (pixel powersupply), such a drop of pixel power supply in driving for initializingthe pixels, for example, in resetting the pixels can be relieved. This,however, increases wiring areas (sensor areas) in the image sensor, andthus, costs.

Therefore, in the present technology, a connection element connects aperipheral circuit that is provided in the vicinity of pixels and doesnot operate in initialization of the pixels, for example, in resettingthe pixels to the pixels, and is turned ON in the initialization of thepixels to temporarily supply power to the pixels. Namely, in theinitialization of the pixels, to the terminals (drains) of resettransistors to which a power supply voltage is applied by a pixel powersupply, the same voltage is applied also from the peripheral circuit.

Herein, examples of the peripheral circuit include a load MOS circuitwhich is a load current source upon selection of the pixel, ADCs (AnalogDigital Converters) which are arranged in a column-parallel manner andconvert electric signals read out from the pixels from analog signalsinto digital signals, and a driver controlling drive of the pixels.Namely, the peripheral circuit may be any circuit provided close to thepixels and performing operation in regard to imaging.

Typically, an image sensor does not basically have a peripheral circuit,which faces the pixels, dynamically operating in a period when thepixels are initialized (reset). Namely, for example, operation ofturning ON or OFF pulse signals (voltage signals) supplied to thepixels, or the like, is not performed. Therefore, during theinitialization period of the pixels, connection of the peripheralcircuit to the pixels does not exert a harmful influence thereon such aspropagation of noise from the peripheral circuit to the pixels.

Moreover, in the present technology, at the end of the initializationoperation of the pixels, the connection element is turned OFF, and thereset transistors in the pixels and the peripheral circuit areelectrically separated from each other in order to prevent noisegenerated in the peripheral circuit from propagating to the pixels.

Thereby, in the present technology, only providing a connection elementconnecting a peripheral circuit to pixels in addition to wirings of animage sensor of the past enables to reduce impedance of the pixelswithout increase of wirings in the pixels and/or wirings from thevicinity of the pixels to the pixels. And thus, the suppression ofincrease in area of the image sensor enables to reduce costs inmanufacturing the image sensor.

[Exemplary Configuration of Solid-State Image Sensor]

Next, a specific embodiment of a solid-state image sensor to which thepresent technology is applied is described.

FIG. 2 is a diagram illustrating an exemplary configuration of oneembodiment of a solid-state image sensor to which the present technologyis applied.

A solid-state image sensor 11 is configured, for example, of a CMOS(Complementary Metal Oxide Semiconductor) image sensor or the like.

The solid-state image sensor 11 includes a pixel circuit 21, a driver22, connection elements 23, a column signal processing part 24 andconnection elements 25.

The pixel circuit 21 includes a plurality of pixels arranged in thehorizontal direction and in the vertical direction in the figure, eachof which pixels performs photoelectric conversion on light from thesubject to generate an electric signal. The pixel circuit 21 outputs theelectric signal obtained from each pixel.

Each of the pixels constituting the pixel circuit 21 includes, forexample, a photoelectric transducer such as a photodiode receiving lightfrom the subject, a floating diffusion region accumulating photochargeobtained by the photoelectric transducer, a transfer transistor fortransferring the charge from the photoelectric transducer to thefloating diffusion region, and the like.

Each pixel, moreover, includes an amplification transistor converting apotential change in the floating diffusion region into an electricsignal, a selection transistor outputting the electric signal read outby the amplification transistor to a vertical signal line connected topixels arranged in the vertical direction, and the like.

Each pixel, furthermore, includes a reset transistor setting thepotential of the floating diffusion region to the level of a resetvoltage by discharging the accumulated charge from the floatingdiffusion region to the outside or by injecting charge from the outsideto the floating diffusion region in initialization of the pixel, forexample, in resetting the pixel. To the drain of the reset transistor, apixel power supply is connected in order to discharge or inject thecharge in the floating diffusion region.

As above, each pixel of the pixel circuit 21 includes the photoelectrictransducer, floating diffusion region, transfer transistor,amplification transistor, selection transistor and reset transistor,whereas the pixel may have any other configuration. Namely, the pixelonly has to include, at least, a configuration for performing thephotoelectric conversion, a configuration for reading out the chargeobtained by the photoelectric conversion as an electric signal, and aconfiguration for initializing the pixel.

The driver 22 is connected to elements constituting each pixel of thepixel circuit 21 via signal lines not illustrated in the figure, andcontrols drive of each pixel with power from the power supply notillustrated in the figure.

For example, the driver 22 applies voltage to the individual gates ofthe transfer transistor, selection transistor and reset transistorconstituting the pixel, and thereby, controls transfer of the charge tothe floating diffusion region, selection of the pixel from which thepixel signal is to be read out, and initialization of the pixel(floating diffusion region).

Moreover, the driver 22 is connected to the individual pixels of thepixel circuit 21 via the plurality of connection elements 23. Eachconnection element 23 is constituted of a switch connecting the pixel ofthe pixel circuit 21 to the power supply, not illustrated in the figure,connected to the driver 22, and applies a power supply voltage to thepixel by switching ON/OFF according to the applied voltage. For example,the terminal of the connection element 23 on the pixel circuit 21 sideis connected to the terminal of the reset transistor constituting thepixel to which the pixel power supply is connected, specifically, to thedrain of the reset transistor. Moreover, the terminal of the connectionelement 23 on the pixel circuit 21 side is also connected to the drainof the amplification transistor.

The column signal processing part 24 is connected to vertical signallines provided for the pixel circuit 21, and supplies a bias current toeach vertical signal line with power from the power supply notillustrated in the figure. Namely, the column signal processing part 24includes a load MOS circuit as a load current source for each pixel.

Moreover, the column signal processing part 24 performs correlateddouble sampling, auto gain control processing, A/D conversion processingand the like based on the electric signal read out from the verticalsignal line in the pixel circuit 21 to generate the pixel signal of eachpixel. Signals constituted of the pixel signals of the individual pixelsthus obtained are to be an image signal of the image obtained by imagingthe subject.

Furthermore, the column signal processing part 24 is connected to theindividual pixels of the pixel circuit 21 via the plurality ofconnection elements 25. Each connection element 25 is constituted of aswitch connecting the pixel of the pixel circuit 21 to the power supply,not illustrated in the figure, connected to the column signal processingpart 24, and applies a power supply voltage to the pixel by switchingON/OFF according to the applied voltage.

For example, the terminal of the connection element 25 on the pixelcircuit 21 side is connected to the terminal of the reset transistorconstituting the pixel to which the pixel power supply is connected,that is, to the drain of the reset transistor. Moreover, the terminal ofthe connection element 25 on the pixel circuit 21 side is also connectedto the drain of the amplification transistor.

[Explanation of Operation of Solid-State Image Sensor]

Next, operation of the solid-state image sensor 11 is described.

Upon starting imaging by the solid-state image sensor 11, first, forseveral pixels in the pixel circuit 21, a selection pulse (voltage) issupplied by the driver 22 to the gates of the selection transistorsconstituting the pixels, and the pixels are set to the state of beingselected, that is, set to the state in which electric signals are to beoutputted from the pixels to the vertical signal lines.

At this stage, the vertical signal lines of the pixel circuit 21 are setto the state of bias currents supplied from the column signal processingpart 24. Moreover, in this state, the switches of the connectionelements 23 and connection elements 25 are turned OFF, and thus, thedriver 22 and column signal processing part 24 are not electricallyconnected to the drains of the reset transistors in the pixels of thepixel circuit 21.

Subsequently, initialization (reset) of the selected pixels is performedwith a reset pulse. Namely, the driver 22 applies the reset pulse(voltage) to the gates of the reset transistors constituting theselected pixels of the pixel circuit 21, and turns ON the gates.

Then, the floating diffusion regions are electrically connected to thepixel power supply via the reset transistors, and the floating diffusionregions, that is, pixels undergo the initialization. In addition, in theinitialization of the pixels, the transfer transistors in the selectedpixels in the pixel circuit 21 are turned OFF and allowed not totransfer charges from the photoelectric transducers to the floatingdiffusion regions.

Moreover, when the gates of the reset transistors are turned ON,voltages are applied to the connection elements 23 and connectionelements 25 to turn ON the switches. Thereby, the terminals (drains) onthe side of the reset transistors to which the pixel power supply isconnected are electrically connected to the driver 22 and column signalprocessing part 24 via the connection elements 23 and connectionelements 25. Namely, the terminals of the rest transistors to whichpredetermined voltages are applied due to the pixel power supply areelectrically connected to a peripheral circuit such as the driver 22 andcolumn signal processing part 24 to which the same voltage is applied.

In other words, the terminals of the reset transistors on the pixelpower supply side are electrically connected to the power supplyconnected to the driver 22 and/or the column signal processing part 24.Herein, the pixel power supply connected to the reset transistors andthe power supply connected to the driver 22 and/or the column signalprocessing part 24 are power supply for the same positive voltage.

As above, the pixels are temporarily connected to the power supply viathe connection elements 23 and/or the connection elements 25, thereby,impedance of the pixels (pixel power supply) can be reduced, and thus, adrop of power supply due to the initialization of the pixels can bereduced.

In addition, during the initialization (reset) period of the pixels, forexample, the reset pulse (voltage) is supplied from the driver 22 to thegates of the reset transistors in the pixels, and/or the bias current issupplied by the column signal processing part 24 to the vertical signallines. During the reset period of the pixels, however, the voltage(pulse) supplied by the driver 22 and/or the column signal processingpart 24 to the elements in the pixels is constant, and dynamic operationsuch as turning ON/OFF the gates is not performed. Accordingly, duringthe reset period of the pixels, it can be regarded that the peripheralcircuit such as the driver 22 and column signal processing part 24 doesnot operate.

Upon resetting the pixels, the driver 22 turns OFF the gates of thereset transistors constituting the selected pixels not to initialize thefloating diffusion regions.

At this stage, the switches of the connection elements 23 and connectionelements 25 are turned OFF, and thus, the terminals of the resettransistors on the pixel power supply side are electrically separatedfrom the driver 22 and column signal processing part 24. Namely, theterminals of the reset transistors on the pixel power supply side areelectrically separated from the power supply connected to the driver 22and/or the column signal processing part 24.

As above, after the initialization of the pixels, the terminals of thereset transistors on the pixel power supply side are separated from thedriver 22 and/or the column signal processing part 24 because readoutoperation of the pixel signals is performed after the initialization ofthe pixels in the solid-state image sensor 11.

In the readout operation, the pixel circuit 21, the driver 22 and columnsignal processing part 24 in its vicinity, and the like operatedynamically. Therefore, if the switches of the connection elements 23and connection elements 25 remain turned ON, noise propagates to thepixels via the power supply of the driver 22 and/or the column signalprocessing part 24.

Hence, in the solid-state image sensor 11, during the initializationperiod of the pixels in which the vicinity of the pixels does notoperate, the switches of the connection elements 23 and connectionelements 25 are turned ON to allow the driver 22 and/or the columnsignal processing part 24 to reduce the impedance of the pixels. Then,when the vicinity of the pixels operates, the switches of the connectionelements 23 and connection elements 25 are turned OFF to suppress thepropagation of the noise to the pixels.

Thereby, the width of the power supply wirings of the pixel circuit 21and/or its vicinity can be left thin, and thus, increase in wiringareas, that is, increase in area of the solid-state image sensor 11 canbe suppressed and impedance of the pixels (pixel power supply) can bereduced. Moreover, the suppression of increase in wiring areas enablesto reduce costs in manufacturing the image sensor (solid-state imagesensor 11).

After initializing the pixels, the pixel signals are read out from thepixels. In addition, at the end of the initialization of the pixels, thegates of the selection transistors are turned ON, and the gates of thetransfer transistors and reset transistors are turned OFF. Moreover, theswitches of the connection elements 23 and connection elements 25 areturned OFF.

In such a state, the column signal processing part 24 reads out voltageson the vertical signal lines as reset levels.

Then, the driver 22 applies a transfer pulse (voltage) to the gates ofthe transfer transistors constituting the selected pixels in the pixelcircuit 21, allowing the charges accumulated in the photoelectrictransducers during the period by the present time to be transferred tothe floating diffusion regions. After that, the gates of the transfertransistors are turned OFF, this allowing the transfer pulse not to beapplied to the gates of the transfer transistors.

Since transferring the charges to the floating diffusion regions allowsthe potentials of the floating diffusion regions to change, the columnsignal processing part 24 reads out the voltages of the vertical signallines as signal levels. Furthermore, the driver 22 turns OFF the gatesof the selection transistors of the selected pixels to separate thepixels from the vertical signal lines.

Moreover, the column signal processing part 24 outputs the differencesbetween the read-out reset levels and signal levels as values of thepixel signals. At this stage, A/D conversion processing and/or auto gaincontrol processing are performed as necessary. After that, thesolid-state image sensor 11 repeats the above-mentioned processing thedesired number of times as switching the selected pixels, and ends theimaging processing.

As above, the solid-state image sensor 11 performs imaging, and outputsan image signal constituted of pixel signals of individual pixels.

In the solid-state image sensor 11, connecting the power supply of thedriver 22 and/or the column signal processing part 24 to the selectedpixels in the initialization of the pixels in order to reduce theimpedance of the pixels enables to reduce a drop of power supply arisingin the initialization of the pixels, for example, as illustrated in FIG.3.

In addition, in FIG. 3, the horizontal direction corresponds to time andthe vertical direction corresponds to voltage. Moreover, the position ofthe arrow RT21 in the horizontal direction in the figure indicates thetime point when the pixels are initialized (reset).

In FIG. 3, the curve C21 indicates voltage of the pixel power supply,that is, voltage at the terminal of the reset transistor on the powersupply side according to time in case where the power supply of thedriver 22 and/or the column signal processing part 24 is not connectedto the selected pixels in the initialization of the pixels. On thecontrary, the curve C22 indicates voltage of the pixel power supplyaccording to time in case where the power supply of the driver 22 and/orthe column signal processing part 24 is connected to the selected pixelsin the initialization of the pixels.

Moreover, the curve C23 indicates voltage of a peripheral circuitdisposed in the vicinity of the pixel circuit 21 such, for example, asthe driver 22 and the column signal processing part 24 according totime, and the polygonal line C24 indicates a voltage signal (pulse)supplied to the connection elements 23 and connection elements 25.

Herein, the voltage of the voltage signal indicated by the polygonalline C24 is the voltage at which the switches constituting theconnection elements 23 and connection elements 25 are turned ON, duringthe period with the curve being convex upward, and is the voltage atwhich the switches are turned OFF, during the other period. In thisexample, the switches constituting the connection elements 23 andconnection elements 25 are turned ON immediately before theinitialization of the pixels.

In the example of FIG. 3, when the power supply of the driver 22 and/orthe column signal processing part 24 is not connected to the selectedpixels in the initialization of the pixels, as indicated by the curveC21, the voltage of the pixel power supply significantly decreases atthe time of the initialization of the pixels, and it takes time untilthe voltage recovers.

On the contrary, when the voltage signal indicated by the polygonal lineC24 is supplied to the connection elements 23 and connection elements 25and the power supply of the driver 22 and/or column signal processingpart 24 is connected to the selected pixels in the initialization of thepixels, the voltage of the pixel power supply changes as indicated bythe curve C22.

Namely, although the voltage of the pixel power supply indicated by thecurve C22 slightly decreases in the initialization of the pixels, thedecrease amount is drastically small compared with that indicated by thecurve C21 and the drop of power supply recovers instantly.

Moreover, in this case, since the power supply of the driver 22 and/orthe column signal processing part 24 is connected to the pixels, thevoltage of the peripheral circuit such as the driver 22 and the columnsignal processing part 24 also slightly decreases in the initializationof the pixels, and after that, recovers immediately as indicated by thecurve C23.

Being apparent from the curve C22 and curve C23, in the solid-stateimage sensor 11, although a slight drop of power supply arises ininitialization of pixels, the drop of power supply recovers instantly,this allowing the solid-state image sensor 11 to operate fast.

Moreover, the voltage of the peripheral circuit indicated by the curveC23 changes upward and downward with a subtle amplitude according tooperation of the peripheral circuit, for example, operation of supplyingvoltage to the elements in the pixels for the readout operation of thesignals from the pixels and the like, after the initialization of thepixels, that is, after the time point indicated by the arrow D11. Sincethe switches constituting the connection elements 23 and connectionelements 25 are turned OFF after the time point indicated by the arrowD11, the noise does not propagate from the peripheral circuit to thepixels.

As above, the power supply of the driver 22 and/or column signalprocessing part 24 is connected to the selected pixels continuouslyduring the initialization period of the pixels, whereas the power supplyonly has to be connected to the pixels during at least part of period inthe initialization period. Specifically, as long as the power supply ofthe driver 22 and/or column signal processing part 24 is connected tothe selected pixels at turning ON the gates of the reset transistors,that is, at the beginning of resetting the pixels, the time point ofending the connection may be before or after ending the initialization.

Moreover, the period in which the power supply of the driver 22 isconnected to the pixels may be same as or different from the period inwhich the power supply of the column signal processing part 24 isconnected to the pixels.

Second Embodiment [Exemplary Configuration of Solid-State Image Sensor]

Incidentally, there is also the case that the power supply voltagesupplied to the peripheral circuit is different from the voltage of thepixel power supply. In such a case, the voltage applied to the pixelsvia the peripheral circuit may be matched with the voltage of the pixelpower supply to connect the peripheral circuit to the pixels, under theconditions that the pixels and the peripheral circuit do notmalfunction.

In this case, the solid-state image sensor is configured, for example,as illustrated in FIG. 4. In addition, the parts corresponding to thosein FIG. 2 are provided with the same reference signs in FIG. 4, andtheir description will be omitted appropriately.

A solid-state image sensor 51 illustrated in FIG. 4 includes a pixelcircuit 21, a driver 22, connection elements 23, a column signalprocessing part 24, connection elements 25, a power supply controlcircuit 61, a connection element 62, a connection element 63, aconnection element 64 and a connection element 65. Namely, thesolid-state image sensor 51 includes a configuration of the solid-stateimage sensor 11 in FIG. 2 additionally provided with the power supplycontrol circuit 61 and the connection element 62 to connection element65.

In this example, a voltage VDD_(pix) of pixel power supply supplied tothe drains of the reset transistors of individual pixels constitutingthe pixel circuit 21 is different in magnitude from a voltage VDD_(peri)of power supply used for driving the pixel circuit 21 by the driver 22and/or column signal processing part 24.

Since the voltage VDD_(pix) is different from the voltage VDD_(peri),for example, the value of the voltage VDD_(pix) is defined in a range inwhich the pixels and the peripheral circuit do not malfunction, or thepixels and/or the peripheral circuit are designed so as not tomalfunction.

The power supply control circuit 61 is a circuit controlling powersupply to the driver 22 and/or the column signal processing part 24 froma power supply not illustrated in the figure, and supplies power to thedriver 22 and/or the column signal processing part 24 in differentvoltages as necessary.

The power supply control circuit 61 and driver 22 are connected to eachother via the connection element 62 and connection element 63constituted of switches and the like.

The connection element 62 and connection element 63 are constituted ofswitches and the like, and supplies power to the driver 22 by turningON/OFF the switches according to the applied voltage.

For example, in the initialization of the pixels, the switch of theconnection element 62 is turned ON, and the switch of the connectionelement 63 is turned OFF. Thereby, in the initialization of the pixels,the power is supplied from the power supply control circuit 61 to thedriver 22 at the same voltage as the voltage of the pixel power supply.

Moreover, during the period except the initialization of the pixels, theswitch of the connection element 62 is turned OFF, and the switch of theconnection element 63 is turned ON, this allowing the power to besupplied from the power supply control circuit 61 to the driver 22 atthe same voltage as the voltage VDD_(peri).

Similarly to the driver 22, the power supply control circuit 61 andcolumn signal processing part 24 are connected to each other via theconnection element 64 and connection element 65 constituted of switchesand the like. The connection element 64 and connection element 65 areconstituted of switches and the like, and supplies power to the columnsignal processing part 24 by turning ON/OFF the switches according tothe applied voltage.

For example, in the initialization of the pixels, the switch of theconnection element 64 is turned ON, and the switch of the connectionelement 65 is turned OFF. Thereby, in the initialization of the pixels,the power is supplied from the power supply control circuit 61 to thecolumn signal processing part 24 at the same voltage as the voltage ofthe pixel power supply VDD_(pix).

Moreover, during the period except the initialization of the pixels, theswitch of the connection element 64 is turned OFF, and the switch of theconnection element 65 is turned ON, this allowing the power to besupplied from the power supply control circuit 61 to the column signalprocessing part 24 at the same voltage as the voltage VDD_(peri).

For example, in the solid-state image sensor 51, the connection element62 and connection element 64 are controlled so as to be turned ON at thetime of turning ON the connection elements 23 and connection elements 25and to be turned OFF at the time of turning OFF the connection elements23 and the connection elements 25. Conversely, the connection element 63and connection element 65 are controlled so as to be turned OFF at thetime of turning ON the connection elements 23 and connection elements 25and to be turned ON at the time of turning OFF the connection elements23 and connection elements 25.

[Explanation of Operation of Solid-State Image Sensor]

The solid-state image sensor 51 as above operates basically same as thesolid-state image sensor 11 in FIG. 2. However, the voltages of thepower supplied in the initialization of pixels and during the periodexcept the initialization of the pixels, respectively, from the powersupply control circuit 61 to the driver 22 and column signal processingpart 24 are switched.

Namely, before the initialization of the pixels, the switches of theconnection element 62 and connection element 64 are turned OFF, and theswitches of the connection element 63 and connection element 65 areturned ON.

Accordingly, the power at the voltage VDD_(peri) is supplied from thepower supply control circuit 61 to the driver 22 and column signalprocessing part 24, and the driver 22 and column signal processing part24 drive the pixel circuit 21 based on the power thus supplied. Forexample, regarding several pixels constituting the pixel circuit 21, thedriver 22 applies a selection pulse at the voltage VDD_(peri) to thegates of the selection transistors constituting the pixels.

In addition, in this state, the switches of the connection elements 23and connection elements 25 are turned OFF.

Then, in the initialization of the pixels, more in detail, immediatelybefore performing the initialization of the pixels, the switches of theconnection element 62 and connection element 64 are turned ON, and theswitches of the connection element 63 and connection element 65 areturned OFF. Thereby, the power at the voltage VDD_(pix) is supplied fromthe power supply control circuit 61 to the driver 22 and column signalprocessing part 24.

At the same time, the switches of the connection elements 23 andconnection elements 25 are turned ON. Thereby, the terminals of thereset transistors on the side to which the pixel power supply isconnected are electrically connected to the driver 22 and column signalprocessing part 24 via the connection elements 23 and connectionelements 25. Namely, the voltage VDD_(pix) is applied from the powersupply control circuit 61 connected to the driver 22 and/or the columnsignal processing part 24 to the terminals of the reset transistors onthe pixel power supply side.

Moreover, at the time of the initialization of the pixels, the driver 22applies a reset pulse (voltage) to the gates of the reset transistorsconstituting the selected pixels of the pixel circuit 21 and turned ONthe gates to initialize the pixels. At this stage, the voltage appliedto the gates of the reset transistors is VDD_(pix).

As above, the pixels are temporarily connected to the power supply viathe connection elements 23 and/or the connection elements 25, thereby,impedance of the pixels can be reduced, and thus, a drop of power supplydue to the initialization of the pixels can be reduced.

The initialization of the pixels is ended by turning OFF the gates ofthe reset transistors constituting the selected pixels by the driver 22.

At this stage, the switches of the connection elements 23 and connectionelements 25 are turned OFF, and the terminals of the reset transistorson the pixel power supply side are electrically separated from thedriver 22 and column signal processing part 24. At the same time, theswitches of the connection element 62 and connection element 64 areturned OFF, and the switches of the connection element 63 and connectionelement 65 are turned ON. Thereby, the power at the voltage VDD_(peri)is supplied from the power supply control circuit 61 to the driver 22and column signal processing part 24.

After the initialization of the pixels is ended and the selected pixelsof the pixel circuit 21 are separated from the power supply of thedriver 22 and column signal processing part 24, readout operation ofpixel signals from the selected pixels is performed.

At this stage, the driver 22 and/or the column signal processing part 24drive the pixel circuit 21 using the power at the voltage VDD_(peri)supplied from the power supply control circuit 61. For example, thedriver 22 supplies a transfer pulse at the voltage VDD_(peri) to thegates of the transfer transistors constituting the pixels to perform thereadout operation of the pixel signals.

As above, the solid-state image sensor 51 switches the voltages of thepower supplied in the initialization period of the pixels and during theperiod except that, respectively, from the power supply control circuit61 to the driver 22 and column signal processing part 24. In theinitialization period of the pixels, the voltage VDD_(pix) differentfrom the voltage VDD_(peri) which is to be applied originally is appliedto the driver 22 and the elements such as the reset transistorsconstituting the pixels of the pixel circuit 21. Therefore, it is thepremise that the peripheral circuit such as the driver 22 and/or thecolumn signal processing part 24 and the pixel circuit 21 do notmalfunction or break at the voltage VDD_(pix).

According to the above-mentioned operation, in the solid-state imagesensor 51, the power supply of the driver 22 and/or the column signalprocessing part 24 is electrically connected to the selected pixels inthe initialization of the pixels, this enabling to reduce impedance ofthe pixels. Thereby, for example, as illustrated in FIG. 5, a drop ofpower supply due to the initialization of the pixels can be reduced.

In addition, in FIG. 5, the horizontal direction corresponds to time andthe vertical direction corresponds to voltage. Moreover, the position ofthe arrow RT31 in the horizontal direction in the figure indicates thetime point when the pixels are initialized.

In FIG. 5, the curve C31 indicates voltage of the pixel power supplyaccording to time in case where the power supply of the driver 22 and/orthe column signal processing part 24 is connected to the selected pixelsin the initialization of the pixels. Moreover, the curve C32 indicatesvoltage of the peripheral circuit disposed in the vicinity of the pixelcircuit 21 such, for example, as the driver 22 or the column signalprocessing part 24 according to time.

Furthermore, the polygonal line C33 indicates a voltage signal (pulse)supplied to the connection elements 23, connection elements 25,connection element 62 and connection element 64. Herein, the voltage ofthe voltage signal indicated by the polygonal line C33 is the voltage atwhich the switches constituting the connection elements 23, connectionelements 25, connection element 62 and connection element 64 are turnedON, during the period with the curve being convex upward, and thevoltage at which the switches are turned OFF, during the other period.

In the example of FIG. 5, the voltage signal indicated by the polygonalline C33 is supplied to the connection elements 23, connection elements25, connection element 62 and connection element 64, and the powersupply of the driver 22 and/or the column signal processing part 24 isconnected to the selected pixels in the initialization of the pixels.Under these conditions, the voltage of the pixel power supply changes asindicated by the curve C31.

Namely, although the voltage of the pixel power supply indicated by thecurve C31 slightly decreases in the initialization of the pixels, thedecrease amount is subtle and the drop of power supply recoversinstantly.

Moreover, in this case, since the power supply of the driver 22 and/orcolumn signal processing part 24 is connected to the pixels, while thevoltage of the peripheral circuit such as the driver 22 and the columnsignal processing part 24 also slightly decreases in resetting thepixels, after that, it recovers immediately as indicated by the curveC32.

Being apparent from the curve C31 and curve C32, in the solid-stateimage sensor 51, although a slight drop of power supply arises inresetting pixels, the drop of power supply recovers instantly, thisallowing the solid-state image sensor 51 to operate fast.

Moreover, the voltage of the peripheral circuit indicated by the curveC32 is VDD_(pix) basically in the initialization period of the pixels,more in detail, during the period in which the switches of theconnection element 62 and connection element 64 are turned ON, andVDD_(peri) during the other period.

Furthermore, the voltage of the peripheral circuit indicated by thecurve C32 changes upward and downward with a subtle amplitude accordingto operation of the peripheral circuit for the readout operation of thesignals from the pixels and the like, after the initialization of thepixels, that is, after the time point indicated by the arrow D21.However, since the switches constituting the connection elements 23 andconnection elements 25 are turned OFF after the time point indicated bythe arrow D21, the noise does not propagate from the peripheral circuitto the pixels.

As above, according to the present technology, pixels are electricallyconnected to power supply of a peripheral circuit during initializationof the pixels and the pixels are separated from the power supply of theperipheral circuit during a period in which the peripheral circuitoperates dynamically, this enabling to suppress increase in area of animage sensor and to reduce impedance of the pixels.

Incidentally, in the above, the peripheral circuit is described,exemplified by the column signal processing part 24 and the driver 22,whereas the peripheral circuit may be any component which is in thevicinity of the pixel circuit 21 and does not operate dynamically ininitialization of the pixels. For example, the peripheral circuit mayinclude a circuit performing correlated double sampling and/or a circuitperforming A/D conversion.

Moreover, in the above, the power supply wirings are exemplarilydescribed which connect the power supply of the peripheral circuit tothe pixel power supply, whereas the present technology is applicable toGND wirings (ground wirings) and/or wirings for negative bias as well asthe power supply wirings. Namely, elements in the pixels to whichelements a predetermined voltage is applied for initializing the pixelsmay be electrically connected to the peripheral circuit to which thesame voltage is applied.

Herein, the predetermined voltage may be any of a positive voltage, anegative voltage and 0 (0 V). For example, in case where the resettransistors constituting the pixels are P-channel MOS transistors, thegrounds of the reset transistors are connected to the ground of theperipheral circuit only during the initialization period of the pixels.

[Exemplary Configuration of Image Capturing Apparatus]

Furthermore, the present technology can be applied to all kinds ofelectronic equipment in which a solid-state image sensor is used as animage acquisition part (photoelectric conversion part) such as an imagecapturing apparatus such as a digital still camera and a video camera, aportable terminal apparatus having an image capturing function, and acopy machine in which a solid-state image sensor is used as an imageacquisition part. The solid-state image sensor may be integrated intoone chip, or may be a module having an image capturing function which ispackaged collectively of an imaging unit and a signal processing unit oran optical system.

FIG. 6 is a diagram illustrating an exemplary configuration of an imagecapturing apparatus as electronic equipment to which the presenttechnology is applied.

An image capturing apparatus 91 in FIG. 6 includes an optical unit 101constituted of lenses and the like, a solid-state image sensor (imagingdevice) 102, and a DSP (Digital Signal Processor) circuit 103 as acamera signal processing circuits. Moreover, the image capturingapparatus 91 further includes a frame memory 104, a display unit 105, arecording unit 106, a manipulation unit 107 and a power supply unit 108.The DSP circuit 103, frame memory 104, display unit 105, recording unit106, manipulation unit 107 and power supply unit 108 are connected toone another via a bus line 109.

The optical unit 101 takes incident light (image light) in from thesubject to image it on the imaging plane of the solid-state image sensor102. The solid-state image sensor 102 converts, for each pixel, thelight amount of the incident light imaged on the imaging plane by theoptical unit 101 into an electric signal to output it as a pixel signal.The solid-state image sensor 102 corresponds to the above-mentionedsolid-state image sensor 11 and solid-state image sensor 51.

The display unit 105 is configured, for example, of a panel displaydevice such as a liquid crystal panel and an organic EL(electroluminescent) panel, and displays a moving image or a still imageimaged by the solid-state image sensor 102. The recording unit 106records the moving image or the still image imaged by the solid-stateimage sensor 102 in a recording medium such as a videotape and a DVD(Digital Versatile Disk).

The manipulation unit 107 issues operation commands for variousfunctions in the image capturing apparatus 91 according to manipulationsof the user. The power supply unit 108 appropriately supplies variouskinds of power supply as operation power supply of the DSP circuit 103,frame memory 104, display unit 105, recording unit 106 and manipulationunit 107.

Moreover, in the above-mentioned embodiments, application to CMOS imagesensors in which pixels are arranged in a matrix shape to detect signalcharges according to light amounts of visible light as physicalquantities is exemplarily described, whereas the present technology isnot limited to the application to such CMOS image sensors but isapplicable to all kinds of solid-state image sensors.

Moreover, the present technology is not limited to application to asolid-state image sensor detecting distribution of incident lightamounts of visible light to image them as a picture, but is applicableto solid-state image sensors imaging distribution of incident amounts ofinfrared rays, X-rays, particles or the like as a picture.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

Additionally, the present technology may also be configured as below.

(1) A solid-state image sensor including:

a pixel circuit including a plurality of pixels and imaging a subject;

a peripheral circuit provided in a vicinity of the pixel circuit andperforming operation in regard to imaging; and

a connection element electrically connecting, in initialization of thepixels, elements in the pixels to which a predetermined voltage isapplied for initializing the pixels to the peripheral circuit with thepredetermined voltage.

(2) The solid-state image sensor according to (1),

wherein the connection element electrically separates the elements fromthe peripheral circuit while the peripheral circuit is performingoperation in regard to imaging, the operation being different from theinitialization of the pixels.

(3) The solid-state image sensor according to (1) or (2),

wherein the predetermined voltage is a positive voltage.

(4) The solid-state image sensor according to (3),

wherein the peripheral circuit is connected to power supply supplyingpower at the predetermined voltage, and

wherein the connection element temporarily connects the elements to thepower supply by connecting the elements to the peripheral circuit in theinitialization of the pixels.

(5) The solid-state image sensor according to (3), further including

a power supply controller supplying power at the predetermined voltageto the peripheral circuit in the initialization of the pixels, andsupplying power at a voltage different from the predetermined voltage tothe peripheral circuit when the peripheral circuit is performing theoperation in regard to imaging, the operation being different from theinitialization of the pixels.

(6) The solid-state image sensor according to (1) or (2),

wherein the predetermined voltage is a negative voltage or zero.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2012-115409 filed in theJapan Patent Office on May 21, 2012, the entire content of which ishereby incorporated by reference.

What is claimed is:
 1. A solid-state image sensor comprising: a pixelcircuit including a plurality of pixels and imaging a subject; aperipheral circuit provided in a vicinity of the pixel circuit andperforming operation in regard to imaging; and a connection elementelectrically connecting, in initialization of the pixels, elements inthe pixels to which a predetermined voltage is applied for initializingthe pixels to the peripheral circuit with the predetermined voltage. 2.The solid-state image sensor according to claim 1, wherein theconnection element electrically separates the elements from theperipheral circuit while the peripheral circuit is performing operationin regard to imaging, the operation being different from theinitialization of the pixels.
 3. The solid-state image sensor accordingto claim 2, wherein the predetermined voltage is a positive voltage. 4.The solid-state image sensor according to claim 3, wherein theperipheral circuit is connected to power supply supplying power at thepredetermined voltage, and wherein the connection element temporarilyconnects the elements to the power supply by connecting the elements tothe peripheral circuit in the initialization of the pixels.
 5. Thesolid-state image sensor according to claim 3, further comprising apower supply controller supplying power at the predetermined voltage tothe peripheral circuit in the initialization of the pixels, andsupplying power at a voltage different from the predetermined voltage tothe peripheral circuit when the peripheral circuit is performing theoperation in regard to imaging, the operation being different from theinitialization of the pixels.
 6. The solid-state image sensor accordingto claim 2, wherein the predetermined voltage is a negative voltage orzero.
 7. A driving method of a solid-state image sensor including apixel circuit having a plurality of pixels and imaging a subject, aperipheral circuit provided in a vicinity of the pixel circuit andperforming operation in regard to imaging, and a connection elementconnecting elements in the pixels to the peripheral circuit, the methodcomprising: electrically connecting, by the connection element, ininitialization of the pixels, the elements in the pixels to which apredetermined voltage is applied for initializing the pixels to theperipheral circuit with the predetermined voltage.